This invention relates to a method for respiratory control by means of neuro-electrical coded signals.
Respiration is a key component of human life. The lungs remove oxygen from air for transport via the blood stream to the entire body. Entrance of air to the lungs must travel through bronchial tubes which can open or close in response to many stimuli. For example, once bronchi constrict and plug with mucus in response to inhaled allergens, as occurs in asthma, the quantity of air is greatly impaired and oxygen starvation begins. Continual evolution of a constricted and mucus filled bronchial tree is always life threatening. This invention offers a way to lower mucus secretion rates and cause dilation of the bronchial tree.
The airways of the lungs begin at the trachea (wind pipe) and move downward where the trachea bifurcates (divides) into the right and left bronchi. As each enters its respective lung it turns into lobar then segmented bronchi. It should be noted that the trachea and the major bronchi are supported by C-shaped cartilaginous hoops. The hoops help maintain the shape of the larger bronchial tubal structures. The “C” is open posteriorly where the bronchial tube is closed by muscle. Bronchial muscle plays an important part in opening and closing bronchial tubes. The evolvement of the bronchial process goes through about 20 reductions in diameter as it continues down to the terminal bronchioles, which are the smallest airways without alveoli.
Bronchi are muscular and can change their lumen (inside) diameter in response to certain stimuli including input from the brain. The terminal bronchi divide into respiratory bronchioles which now have occasional alveoli budding from their walls. Finally, the bronchioles lead to the alveolar ducts that are fully lined with alveoli.
Alveoli, or an alveolus, are tiny sac-like structures where the exchange of oxygen and carbon dioxide occurs. These are commonly called air-sacs. The alveolated region of the lung is known as the respiratory zone. The air filled sacs are lined by flat pneumocytes which secrete a low surface tension surfactant to keep the alveoli patent (open). Only a very thin barrier exists between the pulmonary blood supply and the inspired air where a rapid gas exchange occurs.
The bronchi and air-sacs operate within both lungs. The right lung has 3 lobes and the left lung has 2 lobes. This respiratory system has essentially 2 functions, which are ventilation and gas exchange. The mechanics of breathing consist of inspiration (breathing in) and expiration (breathing out). The driving force for ventilation is the pressure difference between the atmosphere and the intra pulmonic pressure in the alveoli. There are some 300 million alveoli operating in both lungs.
The alveoli are of 2 types. Type I has the shape of a fried egg but with long cytoplasmic (all of the operational contents of a cell except the nucleus) extensions spreading out thinly over the alveolar walls. Type II alveoli are more compact and excrete surfacant by exocytosis. Destruction or injury to type II alveoli leads to a surfactant deficiency which in turn lowers compliance and directly results in pulmonary edema among other complications. As air passes from outside the body into the lungs it is progressively moisturized and when it arrives at the alveoli air is fully saturated with moisture.
The blood supply for the alveoli is provided by an enmeshed dense network of pulmonary capillaries. Carbon dioxide diffuses from the blood into the alveoli where it escapes into the lung spaces while oxygen from the alveoli travels directly into the blood transport over the body.
Many nerves and muscles play a part in efficient breathing. The most important muscle devoted to breathing is the diaphragm. With normal tidal breathing the diaphragm moves about 1 cm, but in forced breathing the diaphragm can move up to 10 cm. The left and right phrenic nerves activate diaphragm movement. The diaphragm is a sheet-shaped muscle which separates the thoriac cavity from the abdominal cavity. Its contraction and relaxation account for a 75% volume change in the thorax during normal quiet breathing. Contracting of the diaphragm as a result of electrical brain signals occurs during inspiration. Expiration happens when the diaphragm relaxes and recoils to its resting position. Indirect influences on inspiration are exerted when the thorax enlarges because of contraction of the scalene and external intercostal muscles. Interestingly, either the diaphragm or the external intercostal muscles can maintain adequate chest cavity movement to maintain adequate ventilation at rest. But during full exertion they are all needed to participate in heavy and rapid breathing. All movements are controlled by electrical nerve signals or waveforms traveling from the brain to the respective muscle structures previously described.
The afferent and efferent nerves travel together and are assisted by afferent lower intercostal nerves in providing information and signals to control the diaphragm in its breathing role. The fourth cranial nerve (trochlear) provides input in operating the diaphragm via the phrenic nerve(s) with assistance from both the third cranial nerve (oculomotor) and the fifth nerve (trigeminal). During normal breathing the expiration process is largely automatic since the lung and chest wall recoil to their normal equilibrium positions. But with inspiration a number of thoriac muscles play a role to expand the lungs and draw in the air. The inspiration process is accomplished by increasing the volume of the chest cavity as the diaphragm muscle contracts.
Control of normal breathing is largely under the direction of the brain stem. However, part of the limbic system of the brain and hypothalamus have the ability to accelerate the pattern of breathing in times of fear or rage. There are chemoreceptors involved in minute-by-minute breathing control which are located in the vicinity of the exit points of the ninth cranial (glossopharyngeal) and tenth cranial (vagus) nerves of the medulla oblongata, near the medulla oblongata's ventral surface.
Additional afferent nerves that arise from sensors that measure blood chemistry act as a sort of status report on how oxygenation is proceeding. The most important are peripheral chemoreceptors located at the bifurcation of the carotid arteries in the neck and also at the heart region in the aorta, above and below the heart's aortic arch. Afferent innervation brings rapid information to the brain to be computed prior to instructing efferent nerves on how to control breathing. The chemoreceptors described are directly involved in how the vagus nerve responds with its own instructional waveform to the bronchi, lungs and heart, all of which are concerned with breathing and blood circulation. There are also mechanoreceptors which measure pressure, vibration and movement that have afferent input to the respiratory and cardiac system. There are also stretch receptors in lungs that tell the brain how the lung is cycling. Also thermal receptors respond to the brain on heat or cold status of the various components. Other inputs to the medulla and the pons area of the brain stem include proprioceptors (a kind of deep sensing related to muscle and tendons) which coordinate muscular activity with respiration. Then there are baroreceptors which send afferent signals to the medullary center as well as to the cardioinhibitory in the medulla to help match pulse rate, blood pressure and respiratory rate in a fine tuning effort necessary for body homeostasis.
The central nervous system (brain) nerves involved in breathing are the second, third, fourth, fifth, eighth, ninth, and the important tenth (vagus) cranial nerves. The first cranial nerve supplies olfactory information and the second and third nerves are related to inputs from the eyes as afferent sensors which integrate what the body is perceiving from outside and demands faster or slower breathing rates or even holding ones breath. The eighth cranial nerve provides auditory afferent input. The various afferent sensory neuro-fibers provide information as to how the body should be breathing in response to events outside the body proper.
An important, even the key, respiratory control, is activated by the vagus nerve and its preganglionic nerve fibers which synapse in ganglia embedded in the bronchi that are also enervated with sympathetic and parasympathetic activity. The sympathetic nerve division can have no effect on bronchi or it can dilate the lumen (bore) to allow more air to enter the respiratory process, which is helpful to asthma patients, while the parasympathetic process offers the opposite effect and is able to constrict the bronchi and increase secretions, which is harmful to asthma patients.